Steam generator coil overheat control



J. D. KIMMEL STEAM GENERATOR COIL OVERHEAT CONTROL Filed Aug. 30, 1967 Dec. 10, 1968 2 Sheets-Sheet 1 FIG] INVENTOR J D KIMMEL ATTORNEY Dec. 10, 1968 .1. 0 KIMMEL STEAM GENERATOR COIL. OVERHEA'I CONTROL 2 Sheets-Sheet 2 Filed Aug. 30, 1967 INVENTOR ATTORNEY United States Patent 3,416,118 STEAM GENERATOR COIL OVERHEAT CONTROL J. D. Kimmel, 1531 Imperial Crown, Houston, Tex. 77043 Continuation-impart of application Ser. No. 507,277, Nov. 12, 1965. This application Aug. 30, 1967, Ser. No. 665,673

6 Claims. (Cl. 337382) ABSTRACT OF THE DISCLOSURE Coil overheat control for steam generators including a differential expansion device for operating a switch means and being integral with the coil of the steam generator.

This application is a continuation-in-part application of my copending application, Ser. No. 507,277, now abandoned, filed on Nov. 12., 1965.

This invention relates to a coil overheat control for steam generators or the like, and more particularly to a coil overheat control that responds directly to the temperature of the coils or pipe and does not depend on the flow through the coils or pipe, although other uses and purposes may be apparent to one skilled in the art.

The coil overheat control of the present invention includes a means responsive to differential expansion between materials of different thermal coefficients of expansion, wherein a tube is integrally connected with the coil or pipe and of the same coefficient of thermal expension, and in which is received a temperature responsive means movable relative to the tube of a lower coeflicient of expansion. A switch responds to the differential expansion of the tube and means within the tube to shut down operation of the steam generator when the average coil or pipe Walltemperatures reach a predetermined temperature.

It is therefore an object of the present invention to provide a new and improved coil overheat control for steam generators.

Another object of the invention resides in the provision of a coil overheat control for steam generators that directly senses the temperature of coils or pipe of the steam generator and does not depend on fluid flow through the coils or pipe.

Still another object of the present invention is in the provision of a coil overheat control for a steam generator that is an integral part of the coils or pipes of the steam generator.

A further object of the present invention is to provide a coil overheat control for steam generators that substantially instantly senses a temperature change in the coils or pipes of the generator.

A still further object of the present invention is in the provision of a coil overheat control for steam generators that is inexpensive and economical to manufacture, simple with a minimum number of parts, and easy to adjust for responding to different temperatures.

Other objects, features and advantages of the invention will be apparent from the following detailed disclosure, taken in conjunction with the accompanying sheets of drawings, wherein like reference numerals refer to like parts, in which:

FIG. 1 is a fragmentary plan view of a set of coils for a steam generator having the coil overheat control of the present invention mounted thereon;

FIG. 2 is an elevational view of the coil overheat control according to the present invention as associated with a coil, with some parts brokenaway for purposes of clarity;

FIG. 3 is a modified coil overheat control according to the present invention;

FIG. 4 is a transverse sectional view taken substantially along line 44 of FIG. 2;

FIG. 5 is a transverse sectional view taken substantially along line 5-5 of FIG. 2;

FIG. 6 is a transverse sectional view taken substantially along line 66 of FIG. 2;

FIG. 7 is a transverse sectional view taken substantially along line 7-7 of FIG. 3; and

FIG. 8 is a transverse sectional view taken substantially along line 88 of FIG. 3.

The coil overheat control of the present invention relies on differential expansion between materials of different thermal coeflicients of expansion for detecting a coil overheat condition in a steam generator. The control is an integral part of the coils or pipes of a steam generator and directly responsive to the temperature of the coils or pipe with which it is associated, and not dependent in any way upon fluid flow through the coils or pipes as heretofore known overheat controls. Thus controls not being a part of the coils or pipes are slow to react as generally they are not in contact with the coils or pipes and therefore depend on radiant heat transfer when no fluid flow is present. Thus, the present invention effectively operates with or without fluid flow to shut down steam generator operation when coils or pipes become overheated to thereby prevent damage to the coils or pipes.

While the invention is illustrated with a single coil or pipe, it can be appreciated that any number of the overheat controls of the present invention may be associated with any one boiler to detect temperatures of coils and/ or pipes, wherein generator shut down may be effected by an overheat condition at any place Where an overheat control is located.

Referring now to the drawings, and particularly to FIG. 1, a coil 10 of a steam generator is illustrated having an inflow connection 11 and an outflow connection 12. An outflow pipe 13 is associated with the outflow connection and has mounted thereon integrally therewith a coil overheating control 14 according to the present invention.

The coil overheat control 14 is shown in FIG. 2 integral with a pipe or coil 15, and includes an elongated sensor tube 16 having a control housing 17 mounted on one end. The tube 16 is mounted to the pipe 15 so that it is essentially integral therewith. As seen more clearly in FIGS. 4, 5 and 6, a slot 15a is milled in the pipe 15 of a size so that the tube 16 may be received therein and welded thereto. In this embodiment the tube is arranged well within the pipe so that in the straight section it is substantially flush with the outer pipe surface. In the embodiment of FIG. 3, the tube 16a protrudes partially within and partially outside of the pipe 46, as seen most clearly in FIGS. 7 and 8. The sensor tube in each embodiment is essentially integral with the pipe, and while directly exposed to the flow through the pipe responds directly to the temperature of the pipe since it is essentially a part of the pipe wall.

The tube 16 is of a material having the same thermal coeflicient of expansion as the pipe 15 and therefore preferably of the same material as the pipe, and includes an elongated bore 18. The tube is closed at the end 19 that is directly associated with the pipe and open at the end that extends within the housing 17. Thus, substantially the entire length of the tube 16 is directly connected to an integral with the pipe 15.

A plurality of lengths or segments of a material, as indicated by the numeral 21, having a thermal coefficient of expansion lower than the tube 16 and the pipe 15 are freely received within the bore 18 of the tube 16. The segments abut against each other and are bottomed at one end against the closed end 19 of the tube and at the other end against an inner follower rod 22 that is in turn in abutment against an outer follower rod 23. The outer follower rod 23 includes a terminal actuating end 24 that extends within the housing 17 Preferably, the segments 21 are of a material having a very low coefiicient of thermal expansion, such a carbon or quartz, and the material is preferably provided in segmental form of about 2 to 3 inches in length so that warping or bending of the pipe 15 will not break these segments. Further, the segments are sized to be freely received within the tube for relative movement thereto.

The housing 17 includes a nipple portion 25 received over the end of the tube 16 and in abutting relation against a nut 26 that is fixed to the tube. A stop nut 27 is threadedly received on the open end of the tube 16 within the housing and serves to hold the housing onto the tube and against the nut 26. Further, a setscrew 28 is provided in the fitting 25 to engage the tube and prevent relative rotation between the housing and the tube.

The terminal end 24 of the outer follower rod 23 abuts against a coarse adjustment screw 29 threadedly received by an arm 30 of a lever 31. A setscrew 32 serves to fix the adjusted position of the coarse adjustment screw 29. The lever 31 is pivotally mounted on a stub shaft 33 carried by the housing. The lever 31 also includes an arm 34 that extends substantially at right angles to the arm 30 and which is provided with a fine adjustment screlw 35 that can be fixed in position by a setscrew 36. A spring 37 is mounted within the housing having one end connected to a pin 38 and the other end connected to the outer free end of the arm 34, whereby the lever 31 is continually urged in a counterclockwise direction to apply a continuous compressive force on the segments 21 and maintain the segments and follower rods in abutting relation. Thus, the segments 21 are continually under compression during operation of the control, whereby differential expansion of the segments and the tube cause movement of the lever 31.

A switch 39 is mounted within the housing, and is preferably of the resettable circuit breaker type, and includes a plunger 40 in alignment with the fine adjustment screw 35, and a reset button 41. Thus, once the switch 39 is actuated, it must be thereafter set to start up the steam generator even after the overheat condition has disappeared due to lowering of the temperature of the pipe 15. A cover plate 42 is removably secured to the housing and may be removed for providing access to the parts within the housing, although it is not necessary to remove the cover to reset the switch 39 since a removable plug 43 is provided in the housing in alignment with the reset button 41.

The burner 44 is diagrammatically shown in connection with the switch 39, whereby the burner and steam generator would be shut down upon actuation of the switch 39 by the lever 31. A conduit fitting 45 is provided in the housing for taking wires from the switch 39 to other terminals in the controls for the steam generator. Thus, if the control is adjusted to shut down steam generator operation when the average coil wall temperatures reach 500 F., such a temperature will cause the differential expansion between the coil and tube to actuate the switch 39 and shut down steam generator operation. Nonmally, one control unit will be provided for each parallel flow steam coil in a steam generator, thereby insuring individual coil protection should there be a stoppage of flow through any one coil. Should the steam generator be shut down by this control, it cannot be restarted until the switch 39 has been manually reset. Such allows the operator to determine why the generator was shut down and gives him a starting point from which to begin troubleshooting.

The embodiment of FIG. 3 operates essentially the same as the embodiment of FIG. 2, but differs in constructional features. The tube 16a is likewise integral (with a coil 46 as above explained, .and provided with a flange 47 that is adapted to mate with a flange 48 carried on a fitting 49 extending from the control housing 50. The follower rod 51 that is in engagement with the segments 21a is provided with a knife edge head 52 in engagement with a slot- 53 at one end of an actuating bar '54. Spaced from the slot 53 and on the opposite side of the bar 54 is a slot 55 that engages a knife edge bearing 56 about which the actuating bar 54 pivots. A spring 57 is bottomed at one end against an inner surface of the housing .and at the outer end against the actuating bar 5 4 to continually urge the bar to pivot in a clockwise direction about the knife edge bearing 56. An adjustable bolt 58 is mounted on the end of the bar 54 opposite the end having the slot 53 for engaging a plunger 59 of a switch 60. A reset button 61 is provided to reset the switch 60 after it has been deenergized. As above mentioned, this embodiment operates in essentially the same manner as the embodiment of FIG. 2 by differential expansion between the tube 16a and the segments 21a.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention, but it is understood that this application is to be limited only by the scope of the appended claims.

The invention is hereby claimed as follows:

1. A coil overheat control in combination with a straight section of steam generator pipe, said pipe having a longitudinally extending slot therein, said control comprising a straight sensor tube closed at one end and open at the other end, said tube having the closed end and substantially all of its length received in said pipe slot so that the length of tube within the pipe is exposed directly to the pipe contents, material welding the slot and tube together, said welding material and said tube closing the slot and forming a part of the pipe wall, said tube having the same coefficient of thermal expansion as said pipe, a control housing mounted on the open end of said tube, means having a coefiiicient of thermal expansion lower than said tube freely received therein and movable relative thereto and bottomed at one end against the closed end thereof, and switch means within said housing drivingly connected to said freely received means and operable in response to differential expansion between said tube and freely received means when said pipe reaches a predetermined temperature.

2. The combination as defined in claim 1, wherein said tube is arranged substantially within the pipe so that it is substantially flush with the outer pipe surface.

3. The combination as defined in claim 1, wherein said tube is arranged partially within and partially outside of the pipe.

4. The combination as defined in claim 1, wherein said switch comprises resettable circuit breaker means.

5. A coil overheat control in combination with a straight section of steam generator pipe, said pipe having a longitudinally extending slot therein, said control comprising a straight sensor tube closed at one end and open at the other end, said tube having the closed end and substantially all of its length received in said pipe slot so that the length of tube within the pipe is exposed directly to the pipe contents, material welding the slot and tube together, said welding material and said tube closing the slot and forming a part of the pipe wall, said tube having the same coefficient of thermal expansion as said pipe, a control housing mounted on the open end of said tube, a follower means slidable in said tube and extending into said control housing, temperature responsive means freely received within said tube and movable relative thereto and bottomed at one end against said follower means and at the other end against the closed end of said tube, means for maintaining said temperature responsive means under compression, said temperature responsive means having a coefiicient of thermal expansion substantially lower than said tube and pipe, and switch means within said housing operable by said follower means in response to differential expansion between said tube and temperature responsive means when said pipe reaches a predetermined temperature.

6. The combination as defined in claim 5, wherein said switch means comprises a resettable circuit breaker.

References Cited UNITED US. Cl. X.R. 

